There has been an increasing interest in the use of biodegradable and/or bioabsorbable materials, rather than biostable biomaterials, in a number of applications in the biomedical field. The importance of biosafety and long-term stability of polymers used in many implants are major driving forces for this trend. The innovations in biomedical processes, such as tissue engineering, gene therapy, controlled drug release, and regenerative medicine have accelerated the use of biodegradable materials to make devices which help the body to repair and regenerate the damaged tissue so that many post or ex-plantation operations can be avoided. Exemplary of the biomedical applications of biodegradable and/or bioabsorbable materials are implants, such as screws, pins, bone plates, staples, sutures (monofilament and multifilament), drug-delivery vehicles, membranes for guided tissue regeneration, mesh and porous materials for tissue engineering, anti-adhesion barriers, tissue scaffolds, cardiovascular grafts, and wound dressings.
One of the key limitations of current biodegradable and/or bioabsorbable materials for many of the potential applications has been the lack of the proper combination of physical properties such as tensile strength, flexibility, elongation, abrasion resistance, etc. for the application. Many of these materials are brittle and are not sufficiently strong for the intended application and there has been significant research toward improving the physical and mechanical properties of these materials through various means, including varying and modifying the chemical structure and blending of these polymers with other polymers to increase their strength, flexibility, and the like.
Polylactic acid (PLA) and polyglycolic acid (PGA) and copolymers of PLA and PGA in particular have good bioabsorbability and biocompatibility, but their physical properties limit their overall suitability for many applications. PLA can be very brittle and so cannot be widely used in many applications, including medical applications, where materials with more robust physical properties are also required. PGA also has poor physical properties, and so cannot be widely used in many applications, including medical applications, where materials with more robust physical properties are also required. Other materials like PLA and PGA, including copolymers of PGA and PLA, and the like, have similar drawbacks. On the other hand, thermoplastic polyurethanes (TPU) have very good physical properties but often have unacceptable bioabsorbability and biocompatibility. There is a need for materials with the good bioabsorbability and biocompatibility of PLA but also the good physical properties of materials like thermoplastic polyurethanes (TPU). There remains a need for biodegradable and/or bioabsorbable polymers to meet a variety of applications where the desired combination of physical properties and degradation rate can be chosen for the biodegradable and/or bioabsorbable polymer tailored to the specification application for which it will be used. The present invention addresses these ongoing needs.